Chemical compositions and method for degassing of processing equipment

ABSTRACT

The use of a chemical composition in degassing of vessels is taught, said chemical composition comprising 1-10% by weight of an oxyalkylated dodecyl thiol; and 1-20% by weight of an alkyl di-substituted 9-decenamide. A method is further provided for degassing a vessel. The method comprises charging said vessel with chemical composition and a carrier medium, wherein said chemical composition comprises 1-10% by weight of an oxyalkylated dodecyl thiol and 1-20% by weight of an alkyl di-substituted 9-decenamide.

FIELD OF THE INVENTION

The present invention relates to chemical cleaning compositions andmethods for removing fouling in the form of hazardous vapors andresidual hydrocarbon liquids from petroleum refining, chemical,petrochemical and manufacturing processing equipment.

BACKGROUND OF THE INVENTION

In the many chemical industries, maintenance and capital improvementsoccur on a scheduled basis. Operating units including various types ofvessels from tanks to towers to heat exchangers to distillation columnsand other types of equipment are maintained as part of an effort calleda turn-around.

During a turn-around, an operating process vessel cannot be merelyshutdown and drained before personnel entry for maintenance. The vesselmust first be decontaminated of any residual materials in it, which mayrender the vessel harmful for workers to enter.

During a turnaround, and before internal mechanical maintenance isperformed of any kind, a cleaning must take place which frees all theinternal surfaces of the process equipment from contaminants. Theseinternal surfaces may include the walls of the vessel cylinder, the topsand bottoms of trays, packing sections (loose or fixed), spargers,pump-around piping, and especially the bottom third of the vessel. Thebottom section is typically very difficult to dean since heavierchemicals tend to settle and accumulate in this area.

The contaminants removed are often hydrocarbons. These hydrocarbons willvary in size, length, molecular weight and structure. The industrycommonly categorizes hydrocarbons into Light ends, Medium cuts and Heavycuts. Light ends would be cuts like methane, propane, ethane, and thelike. Medium cuts would include kerosene, gasoline, and diesel, amongothers. Heavy cuts would include lubricants, waxes and asphalt.

There are several methods for cleaning pressurized vessels known in theprior art including liquid circulation of aqueous solutions of cleaningchemicals and the injection of cleaning chemicals into steam spargedthrough the equipment to effect decontamination. The prevalent processused for decontamination is through steam injection, also calledvapor-phase cleaning.

In vapor-phase cleaning, a chemical is injected into a steam stream thatis sparged through the equipment over a period of time. The chemicalsused for this purpose are often termed as degassing products intendedfor use in the removal of the hazardous gases, such as hydrogen sulfide,ammonia and light hydrocarbons such as benzene. While deemed degassingchemicals, the process is primarily intended to remove residual liquidhydrocarbon oils from the equipment. In doing so, the residual oils thatare the source of gas generation within equipment, are removed therebyallowing for more rapid gas elimination via steam pressure.

Rapid removal of the residual hydrocarbon liquids is an importantcomponent in the time efficient application of the degassing process.Otherwise, residual liquid hydrocarbons volitalize and become the sourceof continued evolution of hazardous vapors. Without the removal of theresidual hydrocarbon liquids, otherwise known as degreasing, thedecontamination process often would require long periods of time, dayseven, before the equipment could be authorized for safe entry.

While simple and relatively inexpensive, the cleaning performance ofhigh-pressure steam is very poor. By itself, the steam process will notreduce the hydrocarbon gas. Therefore, the vessel is usually opened tothe atmosphere until the hydrocarbon gas has volatilized and moved outof the vessel. This airing out process may take as long as two days.

Another method incorporates liquid cleaning with a caustic solution.Caustic solution cleaning begins like the basic steam cleaningmethod—with a reduced crude wash. After the reduced crude wash, causticor high-pH chemicals are circulated through the vessel. Due to the highpH of the caustic chemical, effluent generated during the caustic washmust be neutralized with an add to neutralize the pH before thesignificant quantities of effluent are sent to a wastewater-treatmentplant for processing. Additional processing may be required if thecaustic chemicals contain phosphates, silicates, or other chelatingagents that can interfere with the waste-treatment process.

Yet another method involves an organic solvent wash. This method, likethe first two, begins with a reduced crude wash. Next, organic solventsare circulated through the vessel from top to bottom. Although theseorganic solvents may satisfactorily remove oils, they do not have thesolvency strength necessary to thoroughly clean the vessels while in aliquid phase. Solvent circulation can last as long as 24-48 hours. Afterthe liquid phase cleaning, a water rinse is used to remove organiccontamination from the vessel. Since organics by nature are not watersoluble, rinsing with water is time-consuming, inefficient, and verydifficult. Additionally, it is extremely difficult to determine whetherthese potentially harmful organics have been completely removed by therinse process,

In summary, each of these prior art methods require that the vessel beexposed to the atmosphere to remove harmful gas and then manuallycleaned to remove contamination.

One alternative procedure envisages inertisation of the atmosphereinside the tank before degassing, for example by introducing nitrogen orargon into the tank through tank openings.

As well as being expensive this operation may considerably lengthendegassing times. In fact, inertisation requires the prior sealing of allthe gaskets of the tank, including the legs supporting the mobile roof.The vaporisation of the nitrogen, the dispersion of the nitrogen insideof the tank and periodic tests of control to check the level ofinertisation achieved, all add to the length of the degassing procedure.

U.S. Pat. No. 6,893,509 B2 (Sears et al., 2005) teaches a process ofinjecting a terpene and a surfactant package into high-pressure steam,and introducing the steam and chemistry mixture into the equipment toclean its inside surfaces.

U.S. Pat. No. 8,480,812 (Nath et al., 2013) teaches a cleaning agentcontaining one or more solvents, such as terpenes or other organicsolvents. The cleaning agent is injected into contaminated equipment,along with a carrier gas, in the form of a cleaning vapor. The carriergas may be nitrogen or other inert gases.

WO 2011145122 A1 (2011, Rancich) teaches a method of introducing anatornised aqueous mixture which interacts chemically and/or physicallywith VOC (volatile organic compounds) in the gaseous state inside atank, so as to encourage them to pass from the gaseous phase to theliquid phase, and to remain in the liquid phase. Aqueous mixturecomprises one or rn surfactant substances and chelating substances thataid in VOC absorption.

U.S. Pat. No. 8,491,721 (Ortega et al., 2013) provides a method forcleaning storage tank by mixing a high-powered emulsifying agent withthe residual of water, solids, and trace amounts of hydrocarbons tosubstantially emulsify the hydrocarbons.

U.S. Pat. No. 6,905,577 (Salama, 2005) teaches the use of an electricalcorona discharge reactor capable of producing ozone for the oxidation ofVOC's, as well as other undesirable compounds such as H₂ 5, NH₄,mercaptans, and chlorinated solvents which can be present in gaseouseffluents.

U.S. Pat. No. 5,776,257 (Arnold et al., 1998) Teaches a method ofremoving VOC's from a tank by repetitive spraying of diesel mist whichis allowed to settle. This permits the diesel spray to act as a spongeand remove gaseous airborne VOC's in the tank.

U.S. Pat. No. 20130087511 A1 (Ledebuhr et al., 2013) teaches VOC removalfrom floo,vback water stored in holding tanks. A portion of thecontained water is routed and pumped to an atomizer at the top of thetank in the space above the contained water thus creating a mist of veryfine droplets that capture VOC vapors.

U.S. Pat. No. 5,356,482 (Mehta et al., 1994) teaches a liquid-steammethod using terpenes to detoxify the insides of a vessel to removedangerous and explosive gases. Specifically, it involves use of steamacids alkalies or wetting agents to decontaminate the vessels.

U.S. Pat. No. 5,425,814 (Krajicek et al., 1995) teaches using an aqueoussolution at an elevated temperature, of an extractant, such as aterpene, and a surfactant mixture which extracts and traps contaminants.

U.S. Pat. No. 6,872,263 (Jansen et al., 2005): the present inventionemploys a naturally occurring organic solvent as a cleaning agentinjected directly into one or more high-pressure steam lines alreadypresent in the refinery's system. The cleaning agent and stream mix asvaporized and allowed to enter into the equipment where upon it cleansall surfaces inside the equipment.

SUMMARY

The use of a chemical composition in degassing of vessels is taught,said chemical composition comprising 1-10% by weight of an oxyalkylateddodecyl thiol; and 1-20% by weight of an alkyl di-substituted9-decenamide.

A method is further provided for degassing a vessel. The methodcomprises charging said vessel with chemical composition and a carriermedium, wherein said chemical composition comprises1-10% by weight of anoxyalkylated dodecyl thiol and 1-20% by weight of an alkyldi-substituted 9-decenamide.

It is to be understood that other aspects of the present invention willbecome readily apparent to those skilled in the art from the followingdetailed description, wherein various embodiments of the invention areshown and described by way of illustration. As will be realized, theinvention is capable for other and different embodiments and its severaldetails are capable of modification in various other respects, allwithout departing from the spirit and scope of the present invention.Accordingly the drawings and detailed description are to be regarded asillustrative in nature and not as restrictive.

DETAILED DESCRIPTION OF THE INVENTION

The description that follows and the embodiments described therein areprovided by way of illustration of an example, or examples, ofparticular embodiments of the principles of various aspects of thepresent invention. These examples are provided for the purposes ofexplanation, and not of limitation, of those principles and of theinvention in its various aspects.

The present invention relates to improvements in the degassing ofprocess equipment and vessels to decontaminate them to allow for humanentry, by use of chemical compositions designed to enhance the removalof residual hydrocarbon liquids. The present composition can be appliedin a carrier medium wherein the carrier medium can be in either thevapour or liquid phases.

The present inventors have discovered that a combination of anoxyalkylated thiol and a substituted 9-decenamide when injected withsteam or liquid, produce exemplary performance in degreasing typicalprocessing equipment and thereby significantly reducing the timerequired to decontaminate processing equipment during typical degassingoperations.

The present composition has also been surprisingly found to show goodperformance in degassing, that is removal of the hazardous gases,together with the necessary degreasing, or removal of liquidhydrocarbons, that are both required to sufficiently clean a vessel forhuman entry. The present inventive process can be conducted without theneed for airing out of the vessel or exposing it to atmosphere.

The use of the present composition in degassing applications, whereinthe present composition performs both degassing and degreasing functionsleads to fewer degassing steps, fewer separate chemicals for degassingand degreasing and less time in preparing vessels for human entry. Thepresent composition has shown strong efficacy and efficiency indegassing, reducing degassing time and speeding up the turn-aroundprocess.

The chemical compositions of the present invention may preferablyinclude a vapour absorbent having an affinity for vapor-statehydrocarbons molecules. The optional vapour absorbent aides in theexpedient removal of hazardous gases.

In performing the process of the present invention, the chemicalcomposition as described above can be applied in a number of meansincluding vapour phase application in which either steam or a gas suchas nitrogen carries the composition; and also liquid phase applicationin which the composition is added to water. The water can be any kind ofavailable water source at the processing facility, including firewater.

Liquid circulation involves filling the process equipment substantiallyfully with an aqueous solution of the present composition andcirculating the liquid around the vessel by any known means in the art.Alternative, liquid cascade involves filling the process equipment onlypart way with an aqueous solution of the present composition andspraying the aqueous solution up to a top of the equipment and allowingthe aqueous solution liquid to cascade down the walls of the equipment.Preferably in a liquid cascade application, the process equipment isfilled to about 25-35% of the equipment's volume.

In the case of steam injection the present composition can be injectedin an amount of from about 0.2 to 0.5 pounds of composition per pound ofsteam and preferably from 0.25 to 0.35 pounds of composition per poundof steam.

When added in with a liquid for liquid circulation or liquid cascade,the present composition is added at amounts that preferably result in aneffective concentration from about 1.5% to about 5% by volume andpreferably from about 2.5% to 4% by volume of composition in thecirculating liquid. In embodiments when the present composition isapplied in a liquid phase, the aqueous solution of the presentcomposition liquid is preferably heated, more preferably to atemperature of about 140 F to about 180 F (about 60 C to about 82 C) andmost preferably from about 160 F to 170 F (about 71 C to about 77 C).

In some embodiments, when the processing equipment is a tower, column,or any other large vertical vessel, liquid cascading is a preferred useof the present composition since less volume of the cleaning compositionand circulating liquid needs to be added to these larger vessels. Insuch cases the volume of the present composition and circulating liquidis preferably from about 25% to about 35% of the tower volume.Preferably the circulating liquid is circulated through the towerthrough a circulation loop at a rate sufficient to flood packings andtrays of the tower, most preferably at a minimum rate of 1,000 GPM.

The waste liquid resulting from the spent aqueous solution of thepresent composition in both liquid circulation and liquid cascadingoperations can be sent directly to conventional waste water treatmentwithout the need for additional pre-treatments.

The chemical composition of the present invention comprises:

-   -   a) 1-10% by weight of an oxyalkylated dodecyl thiol; and    -   b) 1-20% by weight of an alkyl di-substituted 9-decenamide.

Preferably the molar percentage of ethylene oxide in the oxyalkylateddodecyl thiol ranges from 45-70% by weight. Further preferably, theconcentration of the oxyalkylated dodecyl thiol in the presentcomposition is 1 to 3% by weight.

Preferably, the alkyl di-substituted 9-decenamide comprises alkyl groupsthat include but are not limited to: dimethyl; dimethyl 1-3 oxo; Cis,9,10 Octa; (Z)octa, 4-hydroxy-3 methoxyphenyl; 2-methyl-3,8-dioxa.Further preferably the alkyl group is in the form of dimethyl groups onthe terminal nitrogen. The concentration of the alkyl di-substituted9-decenamide is more preferably from about 2-5% by weight of the presentcomposition.

The composition of the present invention may also include any number offurther surfactants, pH adjustment agents, hydrotrope agents and otherelements that would be well understood by a person of skill in the artto not detrimentally affect performance of the present composition.There are other ingredients that can be substituted for thenon-essential elements listed below, that can stabilize the mixture andnot negatively affect the performance.

For example, glycol ether may be added with the general formula:

R—(OCH₂CH₂)_(n)OH

-   -   wherein R=methyl, ethyl, butyl, propyl, hexyl        -   n=1,2,3

More preferably, the glycol ether is added to make up 1 to 10% by weightof the chemical composition. Further optionally, a non-ionic surfactantcan be added, preferably to make up from 2-15% by weight of thecomposition. The non-ionic surfactant may preferably be comprised ofC₈-C₁₂ alkylphenol-ethylene oxide adducts, wherein the molar percentageof ethylene oxide ranges preferably from 55-75% and the weightpercentage of the adduct ranges from 10-40%.

Further preferably, 1-10% by weight of a castor oil-ethylene oxideadduct may be added, wherein the adduct is made up of about 60% byweight ethylene oxide. Any number of suitable agents may be used for pHadjustment to a preferable range of 9-11. The pH agent is morepreferably in the form of an alkaline additive that is most preferably amono or diethanolamine. Optionally, any number of suitable hydrotropeagents can also be added to insure uniformity of solution. Preferablythe hydrotrope agent is sodium xylene sulfonate at concentrationssufficient to produce a clear, homogenous liquid typically from about1-10% by weight. Suitable phosphate ester products may be substitutedfor the preferred hydrotroping agent without negative effect onperformance.

The above are illustrative and not intended to limit the scope of thepresent invention. This invention may be embodied in many differentforms and should not be construed as limited to the embodiment set forthabove. It will be recognized by those skilled in the art that othersuitable forms of substituted 9-decenamide may be interchanged for thosematerials herein disclosed and other suitable forms of oxyalkylatedthiol may be substituted without ill effect nor depart from the natureof the invention.

The previous description of the disclosed embodiments is provided toenable any person skilled in the art to make or use the presentinvention. Various modifications to those embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the invention. Thus, the present invention is notintended to be limited to the embodiments shown herein, but is to beaccorded the full scope consistent with the claims, wherein reference toan element in the singular, such as by use of the article “a” or “an” isnot intended to mean “one and only one” unless specifically so stated,but rather “one or more”. All structural and functional equivalents tothe elements of the various embodiments described throughout thedisclosure that are known or later come to be known to those of ordinaryskill in the art are intended to be encompassed by the elements of theclaims. Moreover, nothing disclosed herein is intended to be dedicatedto the public regardless of whether such disclosure is explicitlyrecited in the claims. No claim element is to be construed under theprovisions of 35 USC 112, sixth paragraph, unless the element isexpressly recited using the phrase “means for” or “step for”.

1. Use of a chemical composition in degassing of vessels, said chemicalcomposition comprising: a) 1-10% by weight of an oxyalkylated dodecylthiol; and b) 1-20% by weight of an alkyl di-substituted 9-decenamide.2. The use of claim 1, wherein said composition further comprises analkaline additive to adjust the pH of the composition to a range of from9 to
 11. 3. The use of claim 2, wherein the alkaline additive isselected from a monoethanolamine or diethanolamine.
 4. The use of claim1, wherein said composition further comprises from 1 to 10% by weight ofa glycol ether with the general formula:R—(OCH₂CH₂)_(n)OH wherein R=methyl, ethyl, butyl, propyl, hexyl n=1,2,3.5. The use of claim 1, wherein said composition further comprises from2-15% by weight of a non-ionic surfactant comprised of C₈-C₁₂alkylphenol-ethylene oxide adducts, wherein the molar percentage ofethylene oxide ranges from 55-75% and the weight percentage of theadduct ranges from 10-40%.
 6. The use of claim 1, wherein saidcomposition further comprises 1-10% by weight of a castor oil-ethyleneoxide adduct of about 60% by weight ethylene oxide.
 7. The use of claim1, wherein the alkyl groups of the alkyl di-substituted 9-decenamide areselected from the group consisting of dimethyl; dimethyl 1-3 oxo; Cis,9,10 Octa; (Z)octa, 4-hydroxy-3 methoxyphenyl; 2-methyl-3,8-dioxa. 8.The use of claim 7, wherein the alkyl di-substituted 9-decenamidecomprises a dimethyl group on the terminal nitrogen, as the alkylgroups.
 9. The use of claim 8, wherein the composition comprises fromabout 2% to about 5% by weight of alkyl di-substituted 9-decenamide. 10.The use of claim 1, further comprising a hydrotrope agent that isselected from the group consisting of sodium xylene sulfonate and aphosphate ester product.
 11. The use of claim 10, wherein the hydrotropeagent at a concentration of from about 1% to about 10% by weight. 12.The use of claim 1, wherein the molar percentage of ethylene oxide inthe oxyalkylated dodecyl thiol ranges from 45-70%.
 13. The use of claim12, wherein the concentration of the oxyalkylated thiol in thecomposition is from about 1% to about 3% by weight.
 14. The use of claim1, together with a vapour absorbent having an affinity for vapor-statehydrocarbons molecules.
 15. The use of claim 1, wherein the compositionis injected with steam into a vessel for degassing the vessel.
 16. Theuse of claim 15, wherein the chemical composition is injected in anamount of from about 0.2 to 0.5 pounds of composition per pound ofsteam, into the vessel.
 17. The use of claim 15, wherein the chemicalcomposition is injected in an amount of from 0.25 to 0.35 pounds ofcomposition per pound of steam.
 18. The use of claim 1, wherein thechemical composition is added with a circulating liquid, to the vessel.19. The use of claim 18, wherein the chemical composition is added atamounts of from about 1.5% to about 5% by volume of composition in thecirculating liquid.
 20. The use of claim 18, wherein the chemicalcomposition is added at amounts of from about 2.5% to 4% by volume ofcomposition in the circulating liquid.
 21. The use of claim 18, whereinthe circulating liquid is heated.
 22. The use of claim 21, wherein thecirculating liquid is heated to a temperature of about 140 F to about180 F.
 23. The use of claim 22, wherein the circulating liquid is heatedto a temperature of from about 160 F to 170 F.
 24. The use of claim 18,wherein the vessel to be degassed is a tower and wherein the volume ofthe chemical composition and circulating liquid makes up from about 25%to 35% of the tower volume.
 25. The use of claim 24, wherein thechemical composition and the circulating liquid is circulated throughthe tower at a circulation rate to flood packings and trays of thetower.
 26. The use of claim 25, wherein the chemical composition and thecirculating liquid are circulated at a minimum rate of 1,000 GPM.
 27. Amethod for degassing a vessel, said method comprising a) charging saidvessel with chemical composition and a carrier medium, wherein saidchemical composition comprises 1-10% by weight of an oxyalkylateddodecyl thiol and 1-20% by weight of an alkyl di-substituted9-decenamide.
 28. The method of claim 27, wherein said compositionfurther comprises an alkaline additive to adjust the pH of thecomposition to a range of from 9 to
 11. 29. The method of claim 27,wherein said composition further comprises from 1 to 10% by weight of aglycol ether with the general formula:R—(OCH₂CH₂)_(n)OH wherein R=methyl, ethyl, butyl, propyl, hexyl n=1,2,3.30. The method of claim 27, wherein said composition further comprisesfrom 2-15% by weight of a non-ionic surfactant comprised of C₈-C₁₂alkylphenol-ethylene oxide adducts, wherein the molar percentage ofethylene oxide ranges from 55-75% and the weight percentage of theadduct ranges from 10-40%.
 31. The method of claim 27, wherein saidcomposition further comprises 1-10% by weight of a castor oil-ethyleneoxide adduct of about 60% by weight ethylene oxide.
 32. The method ofclaim 27, wherein the alkyl groups of the alkyl di-substituted9-decenamide are selected from the group consisting of dimethyl;dimethyl 1-3 oxo; Cis, 9,10 Octa; (Z)octa, 4-hydroxy-3 methoxyphenyl;2-methyl-3,8-dioxa.
 33. The method of claim 32, wherein the alkyldi-substituted 9-decenamide comprises a dimethyl group on the terminalnitrogen, as the alkyl groups.
 34. The method of claim 27, wherein thecomposition comprises from about 2% to about 5% by weight of alkyldi-substituted 9-decenamide.
 35. The method of claim 27, furthercomprising a hydrotrope agent that is selected from the group consistingof sodium xylene sulfonate and a phosphate ester product.
 36. The methodof claim 27, wherein the molar percentage of ethylene oxide in theoxyalkylated dodecyl thiol ranges from 45-70%.
 37. The method of claim36, wherein the concentration of the oxyalkylated thiol in thecomposition is from about 1% to about 3% by weight.
 38. The method ofclaim 27, further comprising charging a vapour absorbent having anaffinity for vapor-state hydrocarbons molecules into the vessel.
 39. Themethod of claim 27, wherein the carrier medium is a vapour.
 40. Themethod of claim 39 wherein the vapour medium is steam.
 41. The method ofclaim 40 wherein the vapour medium is an inert gas.
 42. The method ofclaim 40, wherein the chemical composition is injected in an amount offrom about 0.2 to 0.5 pounds of composition per pound of steam, into thevessel.
 43. The method of claim 42, wherein the chemical composition isinjected in an amount of from 0.25 to 0.35 pounds of composition perpound of steam.
 44. The method of claim 27, wherein the carrier mediumis a circulating liquid.
 45. The method of claim 44, wherein thechemical composition is charged in amounts of from 1.5% to 5% by volumeof composition in the circulating liquid.
 46. The method of claim 45,wherein the chemical composition is charged in amounts of from 2.5% to4% by volume of composition in the circulating liquid.
 47. The method ofclaim 44, wherein the circulating liquid is heated.
 48. The method ofclaim 47, wherein the circulating liquid is heated to a temperature ofabout 140 F to about 180 F.
 49. The method of claim 48, wherein thecirculating liquid is heated to a temperature of from about 160 F to 170F.
 50. The method of claim 44, wherein the vessel to be degassed is atower and wherein the tower is charged with chemical composition andcirculating liquid to from about 25% to 35% of the tower volume.
 51. Themethod of claim 44, wherein the chemical composition and the circulatingliquid is circulated through the tower at a minimum circulation rate of1,000 GPM.